JP2014102485A - Optical element for led, and led illumination device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical element that is thin, increases the light utilization efficiency while suppressing the heat deformation, and can reduce the color unevenness, and to provide a low-height LED illumination device using the optical element.SOLUTION: Light emitted from a yellow phosphor 2d of an LED 2 comes from an incidence plane 1a as shown by a solid line, then comes to an outgoing surface 1b, is totally reflected on it, and goes to a bottom surface 1d side. The reflected light is reflected on an outward surface 1go of a recess 1 g, and goes via a flange surface 1f or the outgoing surface 1b. Thus, the light utilization efficiency can be increased and the color unevenness can be suppressed.

Description

  The present invention relates to an LED optical element and an LED illumination device that are installed on the back side of a relatively large area surface member and perform illumination so that light passes through the surface member.

  In a conventional large-sized liquid crystal display device, light from a number of cold-cathode tubes arranged on the back side of the liquid crystal panel is guided to the back side of the liquid crystal panel via a diffusion plate, a reflector, etc., and is uniformly used as a backlight. By illuminating, the image was clearly visible. On the other hand, in recent years, an LED has been used as a light source of a backlight from the viewpoint of energy saving. Further, from the viewpoint that brightness and darkness can be controlled in accordance with an image displayed on the liquid crystal display device, the LED is easy to use, thereby further reducing the power consumption of the liquid crystal display device.

  As described above, when LEDs are used as the backlight of the liquid crystal display device, the LED chip itself is small. Therefore, when such a chip is arranged directly on the back side of the liquid crystal panel, in order to ensure uniform illuminance, countless It is not realistic to need a tip. Therefore, an optical element that converts light emitted from the LED into illumination light with uniform illuminance is necessary. Patent Documents 1 to 3 disclose an optical element for a backlight for liquid crystal that can convert light from an LED into illumination light with as uniform illuminance as possible.

JP 2011-23204 JP 2008-305923 A JP 2009-43628

  Incidentally, an LED that emits white light is used to develop an image displayed on the liquid crystal panel with a natural color. As such an LED that emits white light, a combination of a blue LED chip that emits blue light and a phosphor that emits yellow light by blue light emitted from the blue LED chip is widely used at present. It has been.

  However, the characteristics of a white LED using a blue LED chip and a phosphor include not only the area difference between the chip and the phosphor, but also the lateral chromatic aberration and non-uniformity of the phosphor thickness in white light that has passed through the phosphor. There is a risk of color unevenness called yellow ring centering on the generated optical axis, and when white light with such color unevenness is irradiated on the back of the liquid crystal panel, natural color development of the image displayed on the liquid crystal panel There is a risk of damage.

  In addition, in recent years, it has been desired to reduce the number of LED chips used per unit in order to reduce the cost of backlights for large liquid crystal display devices. When the number of LED chips is reduced in this way, it becomes necessary to increase the amount of light per LED chip (referred to as high power). Furthermore, in order to spread the light emitted from the LED over a wider range, it is desirable that the optical element has a wider range of light distribution characteristics (referred to as high light distribution).

  When the power of the LED chip is increased, the amount of heat generated increases accordingly, which causes a problem of thermal deformation of the optical element. Although glass with high heat resistance can be used for the optical element, polycarbonate may be used which is a resin with high heat resistance because of high cost. Since polycarbonate has a high refractive index, the light emitted from the LED is easy to be totally reflected on the exit surface of the optical element, and the light totally reflected on the exit surface is multiple-reflected inside the optical element to generate light directed toward the liquid crystal panel. Color unevenness may occur. In particular, since the emission angle of the light emitted from the phosphor is wider than the emission angle of the light emitted from the blue LED chip, the light emitted from the phosphor is more likely to be totally reflected on the emission surface of the optical element. As a result, color unevenness is more likely to occur.

  In addition, in order to increase the light distribution of the optical element, there is a method of increasing the curvature (C = 1 / R) of the emission surface of the optical element. Since the incident angle increases, the probability of total reflection increases and color unevenness tends to occur.

  On the other hand, according to the technique of Patent Document 1, light reflected by the light emitting surface of the optical element can be reflected by a plurality of wedge-shaped concave portions provided on the bottom surface and emitted in a direction away from the optical axis. However, the light reflected by the wedge-shaped recess on the radially inner side is incident on the wedge-shaped recess on the outer side in the radial direction, so that light traveling toward the liquid crystal panel may be generated and color unevenness may occur. The color unevenness as in the present invention cannot be solved. Furthermore, since the light reflected by the plurality of wedge-shaped recesses cannot be used as the emitted light, the light utilization efficiency as in the present invention cannot be increased.

  Next, according to the technique of Patent Document 2, the light reflected from the inner surface of the optical element can be reflected by the reflecting surface on the radially outer side and emitted in a direction away from the optical axis. However, the reflecting surface of Patent Document 2 is formed by protruding the incident surface side of the optical element from the center of the optical axis, and has a convex shape. Therefore, a custom-made LED having a thickness larger than usual must be used, resulting in high cost. On the other hand, when a thinner general-purpose LED is used, the reflecting surface comes into contact with the substrate, so that the shape of the reflecting surface must be changed, and there is a problem that the direction of reflected light is limited. In Patent Document 2, the reflecting surface is designed to be thicker than the optical axis direction and the peripheral direction. In the vicinity of the optical axis at the center of the lens, the thickness constituted by the exit surface and the entrance surface is the thinnest part. With these lens configurations, the thickness deviation ratio is deteriorated between the center and the periphery of the lens, which makes it very difficult to mold the lens. Further, in Patent Document 2, since the convex reflection surface is thickened from the optical axis toward the outside, if the reflection surface is brought inward, the outermost peripheral portion is further thinned by increasing the lens thickness. It becomes difficult. That is, it can be seen that the technique of the cited document 2 has a small degree of design freedom with respect to the arrangement of the reflecting surfaces. Further, even if the thickness is constant toward the periphery, the entire volume of the lens is increased and the moldability is deteriorated. Furthermore, when trying to design the lens so that its thickness decreases toward the periphery in order to reduce the volume of the lens, this time, a part of the reflecting surface is directed in the direction of the optical axis and is reflected several times on the reflecting surface. Light traveling in the axial direction is generated, making it very difficult to design without color unevenness. That is, it can be seen that there are various problems in making the reflecting surface convex.

  In addition, in Patent Document 2, since the optical element is directly abutted on the LED to support the optical element, a large amount of heat is transferred to the optical element when the power of the LED chip is increased, and the optical element is thermally deformed. Etc. may occur.

  Further, according to the technique of Patent Document 3, the light reflected by the light emitting surface of the optical element is reflected by the light scattering portion provided on the bottom surface and having a right-angle triangular cross section in the optical axis orthogonal direction. However, although the color unevenness can be improved to some extent by providing the light scattering portion, it is difficult to positively control the color unevenness in a structure in which the reflection surface of the light scattering portion is a flat surface as in Patent Document 3.

  Furthermore, when the light emitted from the LED passes through the light incident surface and then directly enters the light scattering portion, the light may be directed toward the light emission surface. In other words, as in Patent Document 3, when the vertex of the light scattering portion is on the exit side rather than the line connecting the intersection of the entrance surface and the bottom surface and the edge of the outer peripheral surface on the exit surface side The light of 80 to 90 ° emitted almost directly from the light source passes through the light incident surface, and then becomes light directed toward the light emitting surface through the inclined surface of the light scattering portion, resulting in stray light. The problem of causing unevenness occurs.

  Furthermore, in any of the patent documents, the light reflected by the light emitting surface of the optical element is assumed to be light emitted from the center of the LED. According to the research results of the present inventors, the light is emitted from the phosphor of the LED. It has been found that the reflected light is more likely to cause color unevenness when reflected by the exit surface of the optical element, and no countermeasure is described in any patent document.

  The present invention has been made in view of the problems of the prior art, and is an optical element that is thin and capable of improving light use efficiency and improving color unevenness while suppressing thermal deformation and uses the same. An object of the present invention is to provide a low-profile LED lighting device.

  The optical element according to claim 1 is an optical element that is disposed in a non-contact state on the light emitting surface side of the LED, and in which light emitted from the LED is incident, and is emitted from the LED. A light incident surface; a light exit surface that emits light incident from the light incident surface; a bottom surface disposed outside in a direction orthogonal to the optical axis of the light incident surface; and an outer peripheral surface connected to an edge of the bottom surface. The bottom surface is provided with a single concave recess, and the recess comprises a continuous surface having a curvature, and the vertex of the recess is the intersection of the incident surface and the bottom surface when viewed from the direction perpendicular to the optical axis. And a line connecting the edges of the outer peripheral surface on the light exit surface side.

  According to this invention, since it is non-contact with respect to said LED, even if it makes high power of said LED, the heat transfer to the said optical element can be suppressed as much as possible. Further, since the concave portion is formed of a continuous surface having a curvature, particularly when light emitted from the phosphor of the LED is reflected by the emission surface of the optical element, the reflected light is reflected on the relatively wide concave portion. The light can be reflected by a curved surface and emitted in a controlled direction, whereby the light use efficiency can be increased and color unevenness can be suppressed. Further, since the concave portion is single, the light reflected by the surface of the concave portion can be effectively emitted to the outside of the optical element without being blocked. Furthermore, since the concave portion is recessed from the light emitting surface of the LED toward the emitting surface, the optical element can be made thin. And when the vertex of the recess is viewed from the direction orthogonal to the optical axis, it is provided on the bottom surface side than the line connecting the intersection of the incident surface and the bottom surface and the edge on the exit surface side of the outer peripheral surface, The light emitted from the LED at 80-90 ° almost right side and refracted at the entrance surface passes through the exit surface side of the recess, so that it can be prevented from being reflected at the recess and becoming stray light and uneven color. An LED lighting device can be provided.

  Here, the incident surface is a surface on which light emitted from the LED is incident. However, the incident surface is not limited to one surface, and there may be a plurality of surfaces outside the optical axis. The incident surface in this case is a concept including a plurality of surfaces, and the outermost peripheral portion of the incident surface is a position in contact with the bottom surface. Furthermore, the exit surface is an exit surface that emits light incident from the entrance surface, but may have a plurality of surfaces. The bottom surface is a surface that is disposed away from the light emitting surface of the LED in a direction orthogonal to the light axis with respect to the light emitted from the LED, but has a plurality of legs that support the lens. May be. Further, the outer peripheral surface is located at the outermost peripheral portion of the optical element, and may be directly connected to the emission surface, or may have a connecting surface therebetween, or a connecting surface between the bottom surface. You may have. These outer peripheral surfaces (including the connecting surface) may be provided with an angle that intersects the optical axis direction. In the case of having an angle in this way, the amount of light can be increased by using the light positively incident on the outer peripheral surface. In these cases, the connecting surface may be used as a flange. Further, the outer peripheral surface may be a mirror surface and used as an optical surface, in which case it may have a curvature. Preferably, an angle of 0 to 3 ° may be provided for the taper. In addition, a single concave portion is a single concave portion (two in total in the cross section) in each of the bottom surfaces that exist one by one on the left and right with respect to the incident surface (two in total) in the cross section in the optical axis direction of the optical element. Say that exists. In addition, when the bottom surface is viewed from the incident surface side in the optical axis direction, it means that a dent is provided in a donut shape. Furthermore, the apex of the recess means the point that is closest to the exit surface of the surface of the recess in the optical axis direction, and is constituted by the deepest point in the recess when the lens is viewed from the entrance surface. It is a circular part.

  An optical element according to a second aspect is characterized in that, in the invention according to the first aspect, the concave portion has an aspherical shape.

  When the concave portion has an aspherical shape, the light reflected by the incident surface of the optical element can be emitted in a controlled direction with higher accuracy, and color unevenness can be suppressed.

  The optical element according to claim 3 is the invention according to claim 1 or 2, wherein the width of the concave portion in the direction perpendicular to the optical axis is not less than 10% and not more than 50% of the radius of the optical element. It is characterized by that.

  Accordingly, the amount of light that can be reflected by the concave portion can be increased, the light use efficiency can be increased, and the optical element can be stably fixed.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the length of the concave surface on the incident surface side from the apex of the concave portion in the cross section in the optical axis direction of the optical element. Is shorter than the length of the concave portion on the outer peripheral surface side from the apex of the concave portion.

  As a result, the amount of light that can be reflected by the outward surface in the direction orthogonal to the optical axis of the recess can be increased, and the light use efficiency can be increased.

  An optical element according to a fifth aspect is the invention according to any one of the first to fourth aspects, wherein out of the light emitted from the LED and incident from the incident surface of the optical element, the optical axis of the concave portion is outside the orthogonal direction. The light reflected by the orientation surface is directed to the emission surface side from the direction orthogonal to the optical axis.

  Thereby, while being able to implement | achieve high light distribution, color irregularity can be suppressed using the light reflected on the optical axis orthogonal direction outward surface of the said recessed part. Further, color unevenness suppression control can be performed using light reflected by the inward surface in the direction orthogonal to the optical axis of the concave portion.

  An optical element according to a sixth aspect is the invention according to any one of the first to fifth aspects, wherein out of the light emitted from the LED and incident from the incident surface of the optical element, the optical axis of the concave portion is outside the orthogonal direction. The light reflected by the orientation surface passes through the outer peripheral surface of the optical element.

  Control that suppresses color unevenness can be performed using light that has passed through the outer peripheral surface. In addition, after the light radiate | emitted from LED entered into the entrance plane of an optical element on the outer peripheral surface, it may pass through an outer peripheral surface without passing through the output surface of an optical element.

  An optical element according to a seventh aspect is the invention according to any one of the first to sixth aspects, wherein A is a point formed by an edge of the outer peripheral surface on the output surface side in the optical axis direction cross section, and the outer surface is output. A point that intersects the bottom surface or its extended surface when extending in parallel to the optical axis from the point consisting of the edge on the surface side to B is defined as B, and a line segment connecting the point A and the point B is defined as h. In this case, the apex of the recess is provided on the bottom side of a line connecting the point corresponding to h / 2 and the intersection of the incident surface and the bottom surface when viewed from the direction orthogonal to the optical axis. It is characterized by being.

  As a result, the light emitted from the emission surface can be prevented from directly reflecting the light passing through the emission surface of the optical element at the concave portion, and can enter the outer peripheral surface directly from a part of the emission surface. Therefore, the light refracted on the outer peripheral surface can be used as a light source, and the light use efficiency can be further improved.

  An optical element according to an eighth aspect is the invention according to any one of the first to seventh aspects, wherein the optical element is made of acrylic or polycarbonate.

  Acrylic or polycarbonate is excellent in light transmittance. In particular, polycarbonate is particularly effective in the present invention because it is excellent in heat resistance and has a high refractive index.

  The LED illumination device according to claim 9, comprising: an LED; and an optical element that is disposed on the light emission surface side of the LED in a non-contact state with the LED and into which the light emitted from the LED is incident. The LED may be an LED chip that emits light of a first color and a second color different from the first color by the light of the first color emitted from the LED chip. The optical element includes an incident surface on which light emitted from the LED is incident, an emission surface that emits light incident from the incident surface, and light of the light emitted from the LED. A bottom surface disposed away from the light emitting surface of the LED in a direction perpendicular to the optical axis with respect to the axis, and an outer peripheral surface connected to an edge of the bottom surface. A single unit recessed from the light emitting surface to the emitting surface side. The concave portion is formed of a continuous surface having a curvature, and the apex of the concave portion, when viewed from the direction perpendicular to the optical axis, is the intersection of the incident surface and the bottom surface, and the exit surface side of the outer peripheral surface. The light emitted from the phosphor is incident on the incident surface and reflected by the exit surface, and then reflected by the recess. It is characterized by.

  According to this invention, since it is non-contact with respect to said LED, even if it makes high power of said LED, the heat transfer to the said optical element can be suppressed as much as possible. In addition, since the concave portion is formed of a continuous surface having a curvature, particularly when the light emitted from the phosphor of the LED is reflected by the emission surface of the optical element, the reflected light is relatively wide. Can be reflected and emitted in a controlled direction, whereby the light utilization efficiency can be increased and color unevenness can be suppressed. Further, since the concave portion is single, the light reflected by the surface of the concave portion can be effectively emitted to the outside of the optical element without being blocked. Furthermore, since the concave portion is recessed toward the emission surface side from the LED, the optical element can be thinned. And when the recess is viewed from the direction orthogonal to the optical axis, it is provided on the bottom side rather than the line connecting the intersection of the incident surface and the bottom surface and the edge on the exit surface side of the outer peripheral surface. A low-profile LED illuminating device that can suppress light that has been radiated at an angle of 80 to 90 ° and refracted at the incident surface on the exit surface side from the concave portion so that it is reflected by the concave portion and becomes stray light to cause uneven color. Can be provided.

  The LED (Light Emitting Diode) illumination device according to the present invention includes an LED and an optical element.

  Various LEDs can be used, but it is preferable to use a white LED that has a flat light emission surface and emits white light.

  As the white LED, a combination of a blue LED chip and a phosphor such as a YAG phosphor that emits yellow light by blue light emitted from the blue LED chip is preferably used. As white LED, what was described, for example in Unexamined-Japanese-Patent No. 2008-231218 can be used, However, It is not restricted to this.

  Specifically, the white LED includes an LED chip and a phosphor layer formed on the LED chip so as to cover the LED chip. The LED chip emits light of a first predetermined wavelength (light of the first color), and emits blue light in the present embodiment. However, the wavelength of the light emitted from the LED chip of the present invention and the wavelength of the light emitted from the phosphor are not limited, and the light emitted from the LED chip and the light emitted from the phosphor are mixed. As long as the light is a combination of white light, it can be used.

  In addition, as such an LED chip, a well-known blue LED chip can be used. As the blue LED chip, any existing one including InxGa1-xN can be used. The emission peak wavelength of the blue LED chip is preferably 440 to 480 nm. In addition, as a form of the LED chip, the LED chip is mounted on the substrate and directly radiated upward or sideward, or the blue LED chip is mounted on a transparent substrate such as a sapphire substrate, and bumps are formed on the surface thereof. Any form of LED chip, such as a so-called flip chip connection type, in which it is formed and turned over and connected to an electrode on a substrate, can be applied.

  The phosphor layer includes a phosphor that converts light having a first predetermined wavelength emitted from the LED chip into light having a second predetermined wavelength (light of a second color). In an embodiment described later, blue light emitted from the LED chip is converted into yellow light.

  The phosphor used for such a phosphor layer uses an oxide or a compound that easily becomes an oxide at a high temperature as a raw material of Y, Gd, Ce, Sm, Al, La and Ga, and converts them into a stoichiometric amount. The raw material is obtained by thoroughly mixing in a theoretical ratio. Alternatively, a coprecipitated oxide obtained by calcining a solution obtained by coprecipitation of oxalic acid with a solution obtained by dissolving a rare earth element of Y, Gd, Ce, and Sm in an acid at a stoichiometric ratio, and aluminum oxide and gallium oxide. Mix to obtain a mixed raw material. An appropriate amount of fluoride such as ammonium fluoride is mixed with this as a flux and pressed to obtain a molded body. The compact can be packed in a crucible and fired in air at a temperature range of 1350 to 1450 ° C. for 2 to 5 hours to obtain a sintered body having the phosphor emission characteristics.

  The LED is preferably a high power LED. Here, the high-power LED can be composed of an LED having an output of 0.5 watts or more.

  The optical element is preferably made of plastic. As the plastic constituting the optical element, for example, by using polycarbonate, it can be manufactured by injection molding, and the manufacturing cost can be greatly reduced. However, the material is not limited to this.

  According to the present invention, it is possible to provide an optical element that is thin and suppresses thermal deformation, enhances light utilization efficiency, and can improve color unevenness, and a low-profile LED lighting device using the optical element. it can.

(A) is sectional drawing of the optical axis direction of the LED lighting apparatus concerning this Embodiment. (B) is the figure which looked at LED from the light emission surface side. It is sectional drawing of the optical element concerning the comparative example which does not provide the recessed part. It is sectional drawing of the optical element concerning Example 1 which provided the recessed part. It is a graph which takes illuminance on the vertical axis and takes the radius from the optical axis on the horizontal axis. It is a figure which shows the characteristic of the color of the light ray radiate | emitted from the LED illuminating device which has an optical element of FIG.2, 3 concerning Example 1 and Comparative Example 1. FIG. It is a perspective view of the optical element which has a micro pyramid structure which is an example of the surface which has a diffusion effect. FIG. 5 is a diagram illustrating an optical element of Example 2, where (a) is a view seen from the exit surface side, (b) is a cross-sectional view along the optical axis direction VIIB-VIIB, and (c) is a cross-sectional view along the optical axis direction VIIC-VIIC. (D) is the figure seen from the bottom face side. 10 is a graph showing the amount of sag in Example 2. It is a figure which shows the characteristic of the color of the light ray radiate | emitted from the LED illuminating device with an optical element of Example 2. FIG. It is a figure which shows the characteristic of the color of the light ray radiate | emitted from the LED lighting apparatus which has an optical element of the comparative example 2. It is sectional drawing of the optical element concerning a modification.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1A is a sectional view in the optical axis direction of the LED lighting device according to the present embodiment. The LED lighting device according to the present embodiment includes an optical element 1 and an LED 2 formed on a circuit board 3. As shown in FIG. 1B, the LED 2 is a flat structure in which a central LED chip 2c that emits blue light and a circular yellow phosphor 2d provided so as to cover the light emitting side are laminated. It has a light emission surface 2a. The periphery of the light emitting surface 2a is a heat sink 2b having a rectangular shape as a whole. Since the optical element 1 is non-contact with the LED 2, heat transfer to the optical element 1 can be suppressed as much as possible even if the LED 2 is made high power.

  The optical element 1 is formed by molding using polycarbonate or acrylic as plastic. Further, the optical element 1 is disposed on the light emitting side of the LED 2, and has a concave incident surface 1a on which light emitted from the LED 2 is incident, and a generally convex shape that emits light incident from the incident surface 1a to the outside. , The bottom surface 1d facing the substrate 3 outside the LED 2 in the direction perpendicular to the optical axis, the outer peripheral surface 1f that is a cylindrical surface or a conical surface provided on the outer periphery of the output surface 1b, and a connecting surface f2. The outer peripheral surface 1 f and the connecting surface f 2 as flange surfaces are portions where a gate is provided when the optical element 1 is injection-molded.

  The incident surface 1a includes a concave aspherical inner surface 1a1 including the optical axis OA, a tapered outer surface 1a2, and a plane 1a3 connecting them. The exit surface 1b is concave in the vicinity of the optical axis and convex in the periphery, but may be convex as a whole.

  The bottom surface 1d is provided with a single recess (here, an annular groove centered on the optical axis OA) 1g recessed from the LED 2 toward the exit surface 1b. The recess 1g is an aspherical surface having a curvature and is continuous. It consists of the surface. The recess 1g is divided into an optical axis direction outward surface 1go and an inward surface 1gn at the apex P, and the width A of the outward surface 1go is longer than the width B of the inward surface 1gn. A is preferably 0.8 or more. Furthermore, the width (A + B) of the recess 1g with respect to the radius (R) of the optical element is 10% or more and 50% or less. The recess 1g is present on the LED side with respect to the surface TP connecting the edge of the tapered outer surface 1a2 (the point D in contact with the bottom surface 1d) and the edge of the emission surface 1b. Further, in the cross section of FIG. 1, a point formed by the edge of the outer peripheral surface 1f on the emission surface 1b side is A, and when extending from the point A toward the bottom surface 1d in parallel with the optical axis OA, it intersects the extended surface of the bottom surface 1d. Assuming that the point B is the line segment connecting the point A and the point B, the vertex P of the concave portion 1g is the point C corresponding to h / 2 and the incident surface (outside) when viewed from the direction orthogonal to the optical axis. It is provided closer to the bottom surface 1d than the line TP 'connecting the side surface 1a2) and the intersection D of the bottom surface 1d.

  The planar bottom surface 1d can be a rough surface having a diffusion action (having a surface roughness of Ra 0.2 μm or more) by increasing the roughness of the corresponding transfer surface of the mold. In addition to the roughened surface, a surface subjected to graining or roughening, or a shape in which minute pyramid structures are two-dimensionally arranged as shown in FIG. The outer peripheral surface 1f can also be a roughened surface having a diffusion action by increasing the roughness of the corresponding transfer surface of the mold. However, the recess 1g is preferably a mirror surface. In general, the mirror surface is Ra 0.025 μm or less.

  In the present embodiment, the bottom surface 1 d has three legs 1 c at equal intervals in the circumferential direction, and is attached with the legs 1 c in contact with the surface of the substrate 3. By disposing the legs 1c discontinuously in the circumferential direction, the LED 2 is prevented from being sealed, and the wiring of the LED 2 can be pulled out, air permeability and heat dissipation can be ensured. Like the bottom surface 1d, the entire leg portion 1c can be a rough surface having a diffusion action by increasing the roughness of the corresponding transfer surface of the mold. In addition, this invention is not restricted to what has a leg part, It is not necessary to have a leg part.

  In the present embodiment, as indicated by the solid line, the light emitted from the yellow phosphor 2d of the LED 2 is totally reflected and incident on the bottom surface 1d side when entering the exit surface 1b after entering from the entrance surface 1a. Head. The reflected light is reflected by the outward surface 1go of the recess 1g and is emitted through the flange surface 1f or the emission surface 1b. Thereby, the utilization efficiency of light can be improved and color unevenness can be suppressed. Note that the present invention is not limited to the yellow light emitted from the yellow phosphor 2d of the LED 2, but also applies to the blue light emitted from the LED chip 2c.

Example 1
FIG. 2 is a cross-sectional view of an optical element according to a comparative example in which no concave portion is provided, and FIG. 3 is a cross-sectional view of the optical element according to Example 1 in which a concave portion is provided. doing. In the comparative example shown in FIG. 2, the light emitted from the yellow phosphor 2d of the LED 2 and incident from the incident surface is reflected on the emission surface and then repeatedly reflected on the bottom surface, the flange surface, and the like. To exit. In particular, there is a problem that the light distribution is narrow because some of the rays reflected from the bottom surface and the exit surface are directed toward the optical axis. On the other hand, in the embodiment shown in FIG. 3, the light emitted from the yellow phosphor 2d of the LED 2 and incident from the incident surface is reflected by the emitting surface, then reflected by the concave portion, and immediately emitted to the outside of the optical element. To come. Thereby, the light which goes to the optical axis side reduces, and light distribution can be ensured widely.

  FIG. 4 is a graph showing the illuminance distribution of the LED lighting apparatus obtained by the inventor through simulation. The ordinate represents illuminance, the abscissa represents the radius from the optical axis, and no comparison is provided. The characteristic of an example (refer FIG. 2) is shown as a continuous line, and the characteristic of the Example (refer FIG. 3) which provided the recessed part is shown with a dashed-dotted line. As is clear from FIG. 4, the illumination distribution is more uniform in this example than in the comparative example in which no concave portion is provided, and it can be seen that providing the concave portion increases the light distribution and increases the light use efficiency. .

  FIG. 5 is a diagram showing the characteristics of the color of light emitted from the LED illumination device having the optical elements of FIGS. 2 and 3, which is obtained by simulation by the present inventor. FIG. 5B is a graph relating to the X axis of the CIE color system, FIG. 5B is a graph relating to the Y axis of the CIE color system in Comparative Example 1, and FIG. 5C is a graph of the CIE color system in Example 1. FIG. 5D is a graph regarding the Y axis of the CIE color system in Example 1. FIG.

  In FIG. 5, (a) and (c) have x values in the CIE color system on the vertical axis, and (b) and (d) have y values in the CIE color system on the vertical axis. In addition, the horizontal axis from (a) to (d) shows the position of the irradiated surface when the optical axis is zero. The closer the graph of FIG. 5 is to flat, the more uniform the color of the emitted light regardless of the position of the irradiated surface, and the better the characteristics as a backlight.

  Here, when comparing (a) and (c) and (b) and (d) in FIG. 5, the PV of (a) and (b) is 0.11 and 0.18, respectively. On the other hand, PV of (c) and (d) is 0.08 and 0.14, respectively. This is presumably because the yellow component was reduced because the light totally reflected on the exit surface was reflected off the recess and immediately emitted to the outside. That is, it can be seen that by using the optical element according to the embodiment of FIG. 3 having the characteristics shown in FIGS. 5C and 5D, color unevenness called yellow ring centering on the optical axis is suppressed.

(Example 2)
FIG. 7 is a diagram illustrating an optical element according to the second embodiment. The same code | symbol is used about the component similar to Example 1 mentioned above. The numbers in the figure are dimensions (mm). Due to the shape of the exit surface 1b and the recess 1g, the surface between the recess 1g and the outer peripheral surface 1f is shifted from the bottom surface 1d (the surface between the recess 1g and the entrance surface 1a) toward the exit surface 1b with respect to the substrate 3. In such a case, even in such a case, the light reflected by the recess 1g can further pass through the outer peripheral surface 1f, thereby effectively suppressing color unevenness. Further, the bottom surface 1d (the surface between the recess 1g and the incident surface 1a) may be a surface having a diffusing action. As a result, color unevenness can be suppressed by imparting a diffusion effect to light rays that are totally reflected by the exit surface 1b and incident on the bottom surface 1d, light rays that are reflected from the substrate 3 and incident on the bottom surface 1d, and the like.

  In the second embodiment, the inner surface 1a1 of the incident surface 1a is a single aspheric surface, and the exit surface 1b includes a first region 1b1, an outer second region 1b2, and an outer third region 1b3 including the optical axis. It is an aspherical shape consisting of three regions. More specifically, the emission surface 1b includes a first region 1b1 that is recessed around the optical axis, around the optical axis OA, a second region 1b2 outside the first region, and an outermost third region 1b3. . In Example 2, the step between the first region 1b1 and the second region 1b2 is about 4 μm, and the step between the second region 1b2 and the third region 1b3 is about 20 μm, but the region may be continuous. Table 1 shows lens data of Example 2.

In the following (including lens data in the table), a power of 10 (for example, 2.5 × 10 ⁻³ ) may be expressed using E (for example, 2.5 × E−3). When the coordinates of the center of the light emitting surface of the LED light source are the origin, and the optical axis is a line that passes through the origin and is perpendicular to the emitting surface, the optical surface of the optical element is assigned the coefficient shown in Table 1 for each equation. It is formed into an aspherical surface that is axisymmetric about the optical axis, which is defined by the above formula.

  Here, X (H) is the distance from the origin in the optical axis direction, κ is the conical coefficient, Ai is the aspherical coefficient, H is the distance (radius) from the optical axis in the direction perpendicular to the optical axis, and r is the radius of curvature.

  Tables 2A and 2B show sag amount data on the entrance surface and the exit surface of Example 2. In the table, SAG (H) is a coordinate in the optical axis direction at a radius H (unit: mm). FIG. 8 shows the sag amount values of the entrance surface and the exit surface of Example 2 with SAG (H) on the vertical axis and the distance from the optical axis on the horizontal axis.

  FIG. 9 is a diagram showing the color characteristics of light emitted from the LED illumination device having the optical element of FIG. 7 obtained by simulation by the present inventor. FIG. 9A is a CIE table in the second embodiment. 9B is a graph relating to the X axis of the color system, and FIG. 9B is a graph relating to XY of the CIE color system in Example 2. 10A is a graph relating to the X axis of the CIE color system in Comparative Example 2, and FIG. 10B is a graph relating to XY of the CIE color system in Comparative Example 2. The solid line corresponds to the cross section in the Y direction of the coordinate axis shown in FIG. 7A, and the dotted line corresponds to the cross section in the X direction. In Comparative Example 2, the concave portion 1g of Example 2 is replaced with a flat surface at the same level as the bottom surface, and the other shapes are the same as those of Example 2.

  As is apparent from a comparison between FIGS. 9 and 10, in the case of Comparative Example 2, a small peak waveform is generated near the optical axis, which causes color unevenness. On the other hand, in the case of Example 2, the same peak is not noticeable. Thereby, the effect which provides the recessed part 1g was confirmed.

  11, the bottom surface 1d (the surface between the incident surface 1a and the concave portion 1g) is shifted to the emission surface 1b side with respect to the substrate 3 in order to further promote heat convection. In this way, the gap with the substrate 3 can be widened. In such a case, by setting the bottom surface 1d as a surface having a diffusing action, color unevenness can be suppressed even when the LED light source 2 directly enters the surface between the incident surface 1a and the recess 1g.

  The present invention is not limited to the embodiments described in the specification, and other embodiments and modifications are apparent to those skilled in the art from the embodiments and ideas described in the present specification. It is. For example, the present invention can be used not only for a backlight of a liquid crystal display but also as an illumination device for signboard illumination.

DESCRIPTION OF SYMBOLS 1 Optical element 1a Incident surface 1b Outgoing surface 1c Leg part 1d Bottom surface 1f Outer peripheral surface 1g Recessed part 2 LED
2a Light emitting surface 2b Heat sink 3 Circuit board

Claims (9)

An optical element that is disposed in a non-contact state on the light emitting surface side of the LED, and in which the light emitted from the LED is incident,
An incident surface on which light emitted from the LED is incident; an exit surface from which light incident from the incident surface is emitted; a bottom surface disposed outside in the direction perpendicular to the optical axis of the incident surface; and an edge of the bottom surface An outer peripheral surface to be connected,
The bottom surface is provided with a single concave recess,
The concave portion has a continuous surface with a curvature,
The vertex of the concave portion is provided on the bottom surface side from a line connecting the intersection of the incident surface and the bottom surface and the edge on the exit surface side of the outer peripheral surface when viewed from the direction perpendicular to the optical axis. An optical element characterized by the above.   The optical element according to claim 1, wherein the concave portion has an aspherical shape.   3. The optical element according to claim 1, wherein a width of the concave portion in a direction perpendicular to the optical axis is not less than 10% and not more than 50% of a radius of the optical element.   In the cross section in the optical axis direction of the optical element, the length of the concave surface on the incident surface side from the apex of the concave portion is shorter than the length of the concave surface on the outer peripheral surface side from the apex of the concave portion. The optical element in any one of Claims 1-3.   Of the light emitted from the LED and incident from the incident surface of the optical element, the light reflected by the outward surface in the optical axis orthogonal direction of the recess is directed to the output surface side from the optical axis orthogonal direction. The optical element in any one of Claims 1-4.   The light reflected by the outward surface in the direction orthogonal to the optical axis of the concave portion out of the light emitted from the LED and incident from the incident surface of the optical element passes through the outer peripheral surface of the optical element. Item 6. The optical element according to any one of Items 1 to 5.   In the cross section in the optical axis direction, the point formed by the edge on the exit surface side of the outer peripheral surface and the bottom surface when extending from the point formed by the edge on the exit surface side of the outer peripheral surface toward the bottom surface in parallel with the optical axis The point intersecting the extension plane is B, and the line segment connecting the point A and the point B is h, and the apex of the recess corresponds to h / 2 when viewed from the direction perpendicular to the optical axis. The optical element according to claim 1, wherein the optical element is provided on a side closer to the bottom side than a line connecting a point to perform and an intersection of the incident surface and the bottom surface.   The optical element according to claim 1, wherein the optical element is made of acrylic or polycarbonate. An LED illuminating device comprising an LED and an optical element that is arranged in a non-contact state on the light emitting surface side of the LED and on which light emitted from the LED is incident,
The LED includes an LED chip that emits light of a first color and a phosphor that emits a second color different from the first color by the light of the first color emitted from the LED chip. Have
The optical element includes an incident surface on which light emitted from the LED is incident, an emission surface from which light incident from the incident surface is emitted, and an optical axis orthogonal direction to the optical axis of the light emitted from the LED. A bottom surface disposed away from the light emission surface of the LED and an outer peripheral surface connected to an edge of the bottom surface, the light emission surface side of the LED on the light emission surface side. A single concave recess is provided, the recess comprising a continuous surface with curvature,
The vertex of the concave portion is provided on the bottom surface side from a line connecting the intersection of the incident surface and the bottom surface and the edge on the exit surface side of the outer peripheral surface when viewed from the direction orthogonal to the optical axis,
The light emitted from the phosphor is incident from the incident surface, reflected by the exit surface, and then reflected by the concave portion.